1. Field of the Invention
The invention relates to the preparation of citric acid and of its anhydrous or hydrous salts.
2. Description of the Prior Art
In the past, citric acid and its derivatives have been obtained primarily from natural sources such as citrus fruit and production via mycological or fermentation processes. The recovery of citric acid from natural sources is disclosed in U.S. Pat. Nos. 2,027,264; 2,193,904 and 2,396,115. The production of citric acid by mycological processes is disclosed in U.S. Pat. Nos. 2,353,771; 2,739,923; 2,883,329 and 3,335,067.
Citric acid and derivatives such as the alkali metal salts thereof are useful in different ways as exemplified by the following patents. As a plasticizer, U.S. Pat. No. 2,409,703. As a bleaching agent, U.S. Pat. No. 2,529,831. As a food antioxidant, U.S. Pat. No. 2,563,855. As a detergent component, U.S. Pat. No. 2,765,280. Another reference providing useful information in connection with citric acid is Braverman, J. B. S., "Citrus Products", Interscience, New York, 1949, page 333-348.
The production of acetone dicarboxylic acid is discussed by H. Schulte and A. Yarsin, Ber., Vol. 89, page 714 (1956).